Enhancing the efficiency and stability of perovskite solar cells by incorporating CdS and Cd(SCN2H4)2Cl2 into the CH3NH3PbI3 active layer

To improve the charge separation and transport efficiency in perovskite solar cells (PSCs) with a TiO2-based hybrid mesoscopic/planar architecture, CdS and Cd(SCN2H4)(2)Cl-2 are incorporated into the CH3NH3PbI3 active layer through in situ synthesis to prepare CdS: Cd(SCN2H4)(2)Cl-2: CH3NH3PbI3 bulk-heterojunction films for PSCs. The incorporated CdS and Cd(SCN2H4)(2)Cl-2 improve the quality of perovskite films. Moreover, Cd(SCN2H4)(2)Cl-2 can effectively reduce the defect state density on the CH3NH3PbI3 crystal surface, which decreases charge recombination and facilitates charge transport in PSCs. Furthermore, first-principles calculations show that the I atom of CH3NH3PbI3 has a strong interaction with the Cd atom of CdS, which induces interfacial charge redistribution and charge transfer at the CH3NH3PbI3/CdS interface and therefore decreases the energy of the CH3NH3PbI3: CdS composite system, leading to more efficient electron-hole separation and improved structural stability of the perovskite bulk-heterojunction film. For the above reasons, the CdS: Cd(SCN2H4)(2)Cl-2:CH3NH3PbI3 bulk-heterojunction cell shows much higher efficiency and better stability than the PSCs with pure CH3NH3PbI3. The highest efficiency reaches 20.1%, which is 1.16 times that (17.3%) of the PSCs with pure CH3NH3PbI3 and is also much higher than those of previously reported CH3NH3PbI3 PSCs with a compact/mesoporous TiO2 film. Our research results may provide a new understanding for improving the structural stability and performance of PSCs.